The production of therapeutic recombinant proteins and antibodies has been conducted by using animal cells in most cases, and the efforts are being made to increase the efficiency of production.
For example, a suspended host cell line which was pre-adapted in a serum-free medium has been used for the fast selection of a high producer cell line. Also, high-expression vectors and high producer cell lines have continuously been developed to remove or shorten the time required for gene amplification. Efforts have also been made to develop an efficient way by using an automated cell selection device in the initial selection of cell lines.
High producer cell lines show the expression levels of 30 to 80 pcd even without gene amplification, and high producer cell lines can be prepared within 4 months by using high-expression vectors based on matrix attachment region (MAR) or ubiquitous chromatin opening element (UCOE) which is similar to MAR.
The recent studies show that vector optimization is necessary to achieve 3 to 5 g/L antibody productivity within six months. Recently, the possibility of productivity enhancement is suggested by the optimization of a MAR element such as dual-MAR, multiple-MAR, trans-MAR, etc., but there is an ongoing need for a stable vector with improved production efficiency which may be obtained by the introduction of 5′UTR or intron element.